简化Java日期操作的开源项目DATE4J方法

　　本文介绍简化Java日期操作的开源项目DATE4J的方法。

　　以往要使用Java对时间日期进行操作，可能会用到以下的一些类：


　   Date and its subclasses :
　　java.util.Date
　　java.sql.Date
　　java.sql.Timestamp
　　The calendar and time zone classes :
　　java.util.Calendar
　　java.util.GregorianCalendar
　　java.util.TimeZone
　　java.util.SimpleTimeZone (for use with the Gregorian calendar only)
　　The formatting and parsing classes :
　　java.text.DateFormat
　　java.text.SimpleDateFormat
　　java.text.DateFormatSymbols
　　以上这么多类用起来是不是很麻烦呢，现在好了，有了DATE4J，就不用这么麻烦了。

　　下面是一些简单的实例：　


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　　//Examples
　　//Here are some quick examples of using date4j's DateTime class :
　　DateTime dateAndTime = new DateTime("2010-01-19 23:59:59");
　　DateTime dateAndTime = new DateTime("2010-01-19 23:59:59.123456789");
　　DateTime dateOnly = new DateTime("2010-01-19");
　　DateTime timeOnly = new DateTime("23:59:59");
　　DateTime dateOnly = DateTime.forDateOnly(2010,01,19);
　　DateTime timeOnly = DateTime.forTimeOnly(23,59,59,0);
　　DateTime dt = new DateTime("2010-01-15 13:59:15");
　　boolean leap = dt.isLeapYear(); //false
　　dt.getNumDaysInMonth(); //31
　　dt.getStartOfMonth(); //2010-01-01, 00:00:00.000000000
　　dt.getEndOfDay(); //2010-01-15, 23:59:59.999999999
　　dt.format("YYYY-MM-DD"); //formats as '2010-01-15'
　　dt.plusDays(30); //30 days after Jan 15
　　dt.numDaysFrom(someDate); //returns an int
　　dueDate.lt(someDate); //less-than
　　dueDate.lteq(someDate); //less-than-or-equal-to
　　//Although DateTime carries no TimeZone information internally, there are methods that take a TimeZone as a parameter :
　　DateTime now = DateTime.now(someTimeZone);
　　DateTime today = DateTime.today(someTimeZone);
　　DateTime fromMilliseconds = DateTime.forInstant(31313121L, someTimeZone);
　　birthday.isInFuture(someTimeZone);
　　dt.changeTimeZone(fromOneTimeZone, toAnotherTimeZone);
　　//Examples
　　//Here are some quick examples of using date4j's DateTime class :
　　DateTime dateAndTime = new DateTime("2010-01-19 23:59:59");
　　DateTime dateAndTime = new DateTime("2010-01-19 23:59:59.123456789");
　　DateTime dateOnly = new DateTime("2010-01-19");
　　DateTime timeOnly = new DateTime("23:59:59");
　　DateTime dateOnly = DateTime.forDateOnly(2010,01,19);
　　DateTime timeOnly = DateTime.forTimeOnly(23,59,59,0);
　　DateTime dt = new DateTime("2010-01-15 13:59:15");
　　boolean leap = dt.isLeapYear(); //false
　　dt.getNumDaysInMonth(); //31
　　dt.getStartOfMonth(); //2010-01-01, 00:00:00.000000000
　　dt.getEndOfDay(); //2010-01-15, 23:59:59.999999999
　　dt.format("YYYY-MM-DD"); //formats as '2010-01-15'
　　dt.plusDays(30); //30 days after Jan 15
　　dt.numDaysFrom(someDate); //returns an int
　　dueDate.lt(someDate); //less-than
　　dueDate.lteq(someDate); //less-than-or-equal-to
　　//Although DateTime carries no TimeZone information internally, there are methods that take a TimeZone as a parameter :
　　DateTime now = DateTime.now(someTimeZone);
　　DateTime today = DateTime.today(someTimeZone);
　　DateTime fromMilliseconds = DateTime.forInstant(31313121L, someTimeZone);
　　birthday.isInFuture(someTimeZone);
　　dt.changeTimeZone(fromOneTimeZone, toAnotherTimeZone);
　　获取DATE4J.jar请访问DATE4J项目网站：http://www.date4j.net

　　本文来自博客：http://blog.csdn.net/softwave/archive/2010/05/06/5564724.aspx